Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total 80-lb bags
19
Estimated concrete cost
$114
Cubic feet per hole
1.09
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter number of posts.
- 2Enter hole diameter (in).
- 3Enter hole depth (in).
- 4Enter price per 80-lb bag ($).
- 5Read your total 80-lb bags on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Setting fence posts securely means filling the hole around each post with concrete, and the amount depends on hole diameter, depth, and how many posts you're placing. This calculator defaults to a typical setup for 8-foot fence posts — a 10-inch diameter hole 24 inches deep — and multiplies the per-hole concrete volume by your post count to give you a total bag count and cost, so you can buy the right amount before starting.
Worked example
Using the values the calculator loads with:
Inputs
- Number of posts: 10
- Hole diameter: 10 in
- Hole depth: 24 in
- Price per 80-lb bag: 6 $
Results
- Total 80-lb bags: 19
- Estimated concrete cost: $114
- Cubic feet per hole: 1.09
What each field means
Inputs
- Number of posts
- The number of posts used in the calculation. Starts at 10 so you have a working example on load.
- Hole diameter (in)
- The hole diameter used in the calculation, measured in in. Starts at 10 in so you have a working example on load. Accepted range: 6–24 in.
- Hole depth (in)
- The hole depth used in the calculation, measured in in. Starts at 24 in so you have a working example on load. Accepted range: 12–48 in.
- Price per 80-lb bag ($)
- The price per 80-lb bag used in the calculation, measured in $. Starts at 6 $ so you have a working example on load.
Results
- Total 80-lb bags
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Estimated concrete cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Cubic feet per hole
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How deep should an 8-ft fence post hole be?
A common rule is one-third the post's above-ground height, so an 8-ft post typically needs a 24-30 inch deep hole depending on soil and wind load.
How many bags of concrete per fence post?
A standard 10-inch by 24-inch hole takes roughly 2 bags of 80-lb concrete mix, though wider or deeper holes need more — this calculator adjusts automatically.
Should I use gravel at the bottom of the post hole?
Yes, a few inches of gravel improves drainage under the post and helps prevent rot or frost heave, but it doesn't significantly change the concrete volume above it.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). 8 Ft Fence Post Concrete Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/8-ft-fence-post-concrete-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/8-ft-fence-post-concrete-calculator" target="_blank" rel="noopener">8 Ft Fence Post Concrete Calculator — RevenueLab</a> (2026).</p>
Source: [8 Ft Fence Post Concrete Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/8-ft-fence-post-concrete-calculator) (2026).